1. Field of the Invention
This invention relates to a chemical reaction apparatus which is not only applicable to certain fields within the chemical industry such as biotechnology, biochemistry and the like, but is also suitable for carrying out research in biological chemistry, inclusive of microbiology, or various kinds of chemical reaction tests such as a clinical diagnosis. The invention relates more particularly to a chemical reaction apparatus which is adapted to allow chemical reaction in a capillary tube so that a reaction test may be made in a simple and efficient manner.
2. Description of the Related Art
In general, methods and apparatus for performing a chemical reaction by the use of many samples each in a small quantity have recently shown rapid progress in the development of techniques in the domain of clinical diagnosis for use with immunochemical reactions. One of these methods has proposed the fixing of an immunoreactive substance on a tiny bead of plastic.
Other methods have been disclosed in such printed publications as European Patent Publication No. 0182221-A2, the inventor of which is also that of the instant application. A reaction container for use with the apparatus in which the aforementioned method is carried out employs test tubes which are tilted and rotated such as to significantly reduce the reaction time. This will fulfil the object of automatically treating many objects to be tested at a higher speed.
Arts and apparatus using capillary tubes have been suggested for performing an immunoreaction, one of which is disclosed in, for example, International Publication (PCT) No. W083/01119. The apparatus according to this PCT invention is fabricated in such a manner that a plurality of capillary tubes are vertically mounted on the periphery of a rotary bed to allow, an immunoreaction to be performed in the capillary tubes. The advantages derived from this apparatus lie in the fact that it is simple and compact since a rapid reaction in the capillary tubes eliminates the need for a stirring means.
When the blood of a patient is used as a sample as in an immunoreaction, tests on a given volume of blood have to be made for many items so that the volume of blood to be used for one item is gradually reduced. However, the aforementioned apparatus for performing a reaction in capillary tubes has an advantage in that a small volume sample is adequate to be useful as compared with the conventional apparatus.
The method for use with a tiny plastic bead is suitable for mass production wherein immunoreactive substances are themselves coated to be the surface thereof. The use of a bead for performing many immunoreactions requires a complicated series of operations such as casting the bead in the test tube, taking out the bead to wash from the test tube, recasting the bead and adding a reagent thereto and so on. For accommodating this, various approaches have heretofore been made. For instance, various automatic mechanisms have been proposed but they have required a complicated mechanism and much time for the reaction. They are not suitable for treatment of many specimens at a high rate.
The European Patent Publication No. 0182221-A2 discloses an apparatus which employs instead of the bead mentioned above a test tube on the inner surface of which the immunoreactive substance is coated, the test tube being tilted and rotated to significantly reduce the reaction time required. An apparatus of this class is most suitable for the purpose of automatically treating many specimens at a high rate as compared with the method for use with a bead.
However, this will render the operation of fixing the immunoreactive substance on the inside of the test tube very complicated and production costs will become high as compared with use of the surface of the bead. More specifically, this operation requires injection of a solution of the immunoreactive substance in a given quantity into the test tube such as to leave it as it is for a given time, and then removal of the solution from the inside, washing and drying the test tube, and so on. In contrast, according to the bead method, the object is effectively attained by casting many beads in the solution of the immunoreactive substance, and the subsequent washing and drying are readily facilitated to be made this method suitable for mass production For clinical examination, however the bead method is inconvenient to the user but ready for production whereas the tube method is convenient to the user but complicated in manufacture.
An operation for coating the immunoreactive substance on the inner surface of a capillary tube is very simple and easy as compared with the test tube operation. More specifically, it is similar in manner to the bead method in that a bundle of capillary tubes is vertically immersed in a solution of the immunoreactive substance so that the capillary tubes are readily filled with the solution from their lower ends to the center thereof. The capillary tubes are left as they are for a given time and at a certain temperature, and are then taken out for the washing and drying steps. Although the immunoreactive substance is coated to the exterior of the capillary tubes, the reaction may be performed without any difficulty when they are used with only the insides thereof involved in the reaction. And the capillary tube has a smaller diameter than that of the test tube so that the volume ratio of the coated immunoreactive substance to a liquid specimen is increased, resulting in a very quick reaction, and thereby eliminating the need for rotation of the test tube in order to facilitate the reaction as is necessary in the test tube method. For this reason, if an apparatus is devised which uses the capillary tubes such as to positively and simply handle a many specimens in an automatic manner, the capillary tube itself is tiny and the machine can thus be made compact so that quick mass treatment may be accomplished at a high treatment rate.
International Publication (PCT) No. W083/0119 discloses an apparatus for use with capillary tubes which employs a combination of coating the immunoreactive substance on the inner surface of the capillary tube and an automatic machine for successively performing the immunoreaction such as to improve on the well known method for coating various chemical substances to the inner surface of the capillary tube.
The apparatus disclosed in the aforementioned publication is constructed such that each of the capillary tubes is always held vertically for various operations. With this arrangement, when the reagent liquid to be charged in the capillary tube is increased the surface tension in the capillary tube cannot sustain the weight of the liquid even if the amount of the liquid is very small. Consequently a portion of the liquid flows out of the tube, thus preventing the apparatus from the performing an accurate chemical reaction.
When each of the capillary tubes is made of hydrophilic material such as glass and the lower end of each of the tubes is in contact with the surface of water, water is sucked into the tube by a capillary phenomenon and rises therein. The water rises to a level inversely proportional to the inner diameter of the tube. This will be shown in the following table prepared by the inventors of the subject application on the basis of their experiments.
TABLE ______________________________________ inner diameter (mm) of glass raised level capillary tube (mm) of water ______________________________________ 1.7 9.5 1.3 10.5 0.95 18.0 ______________________________________
The length of the vertically held capillary tube which is capable of sustaining liquid with which it is completely filled is limited to what is shown in the table. The capillary tube to be used in the apparatus disclosed in the aforementioned publication thus must be quite short.
Sample and reagent liquids may be injected into each of the capillary tubes vertically held in this apparatus in such a manner that the liquid contained in a cup mounted on the top of the tube contacts the tube through perforation formed in the bottom of the cup.
In this connection, a longer capillary tube holds the liquid only in the lower portion thereof. Even if the capillary tube is short, the liquid drops fall from the lower end of the tube or are suspended therefrom when the volume of the liquid contained in the cap is more than the capacity of the tube. Thus, the volume of liquid which drains into a measuring system is inaccurate in quantity. In order to attain accuracy, an accurate micropump needs to be provided. It is, therefore, difficult to secure simplicity of structure with use of a capillary tube instead of a micropump as proposed in the aforementioned publication. Since an extremely short capillary tube has to be used, the mechanism for handling such capillary tube is necessarily complicated. Further, in the aforementioned apparatus, the capillary tube is held vertically and mounted on the periphery of the rotary base as a conveyor device. A specific device is required for mounting the tube and troubles are then involved in mounting and demounting the tube.